/*
* Reimplementation of Deflate (RFC1951) compression. Adapted from
* the version in PuTTY, and extended to write dynamic Huffman
* trees and choose block boundaries usefully.
*/

/*
* TODO:
* 
*  - Feature: could do with forms of flush other than SYNC_FLUSH.
*    I'm not sure exactly how those work when you don't know in
*    advance that your next block will be static (as we did in
*    PuTTY). And remember the 9-bit limitation of zlib.
*     + also, zlib has FULL_FLUSH which clears the LZ77 state as
* 	 well, for random access.
*
*  - Compression quality: chooseblock() appears to be computing
*    wildly inaccurate block size estimates. Possible resolutions:
*     + find and fix some trivial bug I haven't spotted yet
*     + abandon the entropic approximation and go with trial
* 	 Huffman runs
*
*  - Compression quality: see if increasing SYMLIMIT causes
*    dynamic blocks to start being consistently smaller than it.
*     + actually we seem to be there already, but check on a
* 	 larger corpus.
*
*  - Compression quality: we ought to be able to fall right back
*    to actual uncompressed blocks if really necessary, though
*    it's not clear what the criterion for doing so would be.
*/

/*
* This software is copyright 2000-2006 Simon Tatham.
*
* Permission is hereby granted, free of charge, to any person
* obtaining a copy of this software and associated documentation
* files (the "Software"), to deal in the Software without
* restriction, including without limitation the rights to use,
* copy, modify, merge, publish, distribute, sublicense, and/or
* sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following
* conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
* OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT.  IN NO EVENT SHALL THE COPYRIGHT HOLDERS BE
* LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
* IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/

#include <stdio.h>
#include <stddef.h>
#include <string.h>
#include <stdlib.h>
#include <assert.h>

#include "deflate.h"

#define snew(type) ( (type *) malloc(sizeof(type)) )
#define snewn(n, type) ( (type *) malloc((n) * sizeof(type)) )
#define sresize(x, n, type) ( (type *) realloc((x), (n) * sizeof(type)) )
#define sfree(x) ( free((x)) )

#define lenof(x) (sizeof((x)) / sizeof(*(x)))

#ifndef FALSE
#define FALSE 0
#define TRUE (!FALSE)
#endif

/* ----------------------------------------------------------------------
* This file can be compiled in a number of modes.
* 
* With -DSTANDALONE, it builds a self-contained deflate tool which
* can compress, decompress, and also analyse a deflated file to
* print out the sequence of literals and copy commands it
* contains.
* 
* With -DTESTMODE, it builds a test application which is given a
* file on standard input, both compresses and decompresses it, and
* outputs the re-decompressed result so it can be conveniently
* diffed against the original. Define -DTESTDBG as well for lots
* of diagnostics.
*/

#if defined TESTDBG
/* gcc-specific diagnostic macro */
#define debug_int(x...) ( fprintf(stderr, x) )
#define debug(x) ( debug_int x )
#else
#define debug(x) ((void)0)
#endif

#ifdef STANDALONE
#define ANALYSIS
#endif

#ifdef ANALYSIS
int analyse_level = 0;
#endif

/* ----------------------------------------------------------------------
* Basic LZ77 code. This bit is designed modularly, so it could be
* ripped out and used in a different LZ77 compressor. Go to it,
* and good luck :-)
*/

struct LZ77InternalContext;
struct LZ77Context {
  struct LZ77InternalContext *ictx;
  void *userdata;
  void (*literal) (struct LZ77Context * ctx, unsigned char c);
  void (*match) (struct LZ77Context * ctx, int distance, int len);
};

/*
* Initialise the private fields of an LZ77Context. It's up to the
* user to initialise the public fields.
*/
static int lz77_init(struct LZ77Context *ctx);

/*
* Supply data to be compressed. Will update the private fields of
* the LZ77Context, and will call literal() and match() to output.
* If `compress' is FALSE, it will never emit a match, but will
* instead call literal() for everything.
*/
static void lz77_compress(struct LZ77Context *ctx,
                          const unsigned char *data, int len, int compress);

/*
* Modifiable parameters.
*/
#define WINSIZE 32768		       /* window size. Must be power of 2! */
#define HASHMAX 2039		       /* one more than max hash value */
#define MAXMATCH 32		       /* how many matches we track */
#define HASHCHARS 3		       /* how many chars make a hash */

/*
* This compressor takes a less slapdash approach than the
* gzip/zlib one. Rather than allowing our hash chains to fall into
* disuse near the far end, we keep them doubly linked so we can
* _find_ the far end, and then every time we add a new byte to the
* window (thus rolling round by one and removing the previous
* byte), we can carefully remove the hash chain entry.
*/

#define INVALID -1		       /* invalid hash _and_ invalid offset */
struct WindowEntry {
  short next, prev;		       /* array indices within the window */
  short hashval;
};

struct HashEntry {
  short first;		       /* window index of first in chain */
};

struct Match {
  int distance, len;
};

struct LZ77InternalContext {
  struct WindowEntry win[WINSIZE];
  unsigned char data[WINSIZE];
  int winpos;
  struct HashEntry hashtab[HASHMAX];
  unsigned char pending[HASHCHARS];
  int npending;
};

static int lz77_hash(const unsigned char *data)
{
  return (257 * data[0] + 263 * data[1] + 269 * data[2]) % HASHMAX;
}

static int lz77_init(struct LZ77Context *ctx)
{
  struct LZ77InternalContext *st;
  int i;

  st = snew(struct LZ77InternalContext);
  if (!st)
    return 0;

  ctx->ictx = st;

  for (i = 0; i < WINSIZE; i++)
    st->win[i].next = st->win[i].prev = st->win[i].hashval = INVALID;
  for (i = 0; i < HASHMAX; i++)
    st->hashtab[i].first = INVALID;
  st->winpos = 0;

  st->npending = 0;

  return 1;
}

static void lz77_advance(struct LZ77InternalContext *st,
                         unsigned char c, int hash)
{
  int off;

  /*
  * Remove the hash entry at winpos from the tail of its chain,
  * or empty the chain if it's the only thing on the chain.
  */
  if (st->win[st->winpos].prev != INVALID) {
    st->win[st->win[st->winpos].prev].next = INVALID;
  } else if (st->win[st->winpos].hashval != INVALID) {
    st->hashtab[st->win[st->winpos].hashval].first = INVALID;
  }

  /*
  * Create a new entry at winpos and add it to the head of its
  * hash chain.
  */
  st->win[st->winpos].hashval = hash;
  st->win[st->winpos].prev = INVALID;
  off = st->win[st->winpos].next = st->hashtab[hash].first;
  st->hashtab[hash].first = st->winpos;
  if (off != INVALID)
    st->win[off].prev = st->winpos;
  st->data[st->winpos] = c;

  /*
  * Advance the window pointer.
  */
  st->winpos = (st->winpos + 1) & (WINSIZE - 1);
}

#define CHARAT(k) ( (k)<0 ? st->data[(st->winpos+k)&(WINSIZE-1)] : data[k] )

static void lz77_compress(struct LZ77Context *ctx,
                          const unsigned char *data, int len, int compress)
{
  struct LZ77InternalContext *st = ctx->ictx;
  int i, hash, distance, off, nmatch, matchlen, advance;
  struct Match defermatch, matches[MAXMATCH];
  int deferchr;

  /*
  * Add any pending characters from last time to the window. (We
  * might not be able to.)
  */
  for (i = 0; i < st->npending; i++) {
    unsigned char foo[HASHCHARS];
    int j;
    if (len + st->npending - i < HASHCHARS) {
      /* Update the pending array. */
      for (j = i; j < st->npending; j++)
        st->pending[j - i] = st->pending[j];
      break;
    }
    for (j = 0; j < HASHCHARS; j++)
      foo[j] = (i + j < st->npending ? st->pending[i + j] :
      data[i + j - st->npending]);
    lz77_advance(st, foo[0], lz77_hash(foo));
  }
  st->npending -= i;

  defermatch.len = 0;
  deferchr = '\0';
  while (len > 0) {

    /* Don't even look for a match, if we're not compressing. */
    if (compress && len >= HASHCHARS) {
      /*
      * Hash the next few characters.
      */
      hash = lz77_hash(data);

      /*
      * Look the hash up in the corresponding hash chain and see
      * what we can find.
      */
      nmatch = 0;
      for (off = st->hashtab[hash].first;
        off != INVALID; off = st->win[off].next) {
          /* distance = 1       if off == st->winpos-1 */
          /* distance = WINSIZE if off == st->winpos   */
          distance =
            WINSIZE - (off + WINSIZE - st->winpos) % WINSIZE;
          for (i = 0; i < HASHCHARS; i++)
            if (CHARAT(i) != CHARAT(i - distance))
              break;
          if (i == HASHCHARS) {
            matches[nmatch].distance = distance;
            matches[nmatch].len = 3;
            if (++nmatch >= MAXMATCH)
              break;
          }
      }
    } else {
      nmatch = 0;
      hash = INVALID;
    }

    if (nmatch > 0) {
      /*
      * We've now filled up matches[] with nmatch potential
      * matches. Follow them down to find the longest. (We
      * assume here that it's always worth favouring a
      * longer match over a shorter one.)
      */
      matchlen = HASHCHARS;
      while (matchlen < len) {
        int j;
        for (i = j = 0; i < nmatch; i++) {
          if (CHARAT(matchlen) ==
            CHARAT(matchlen - matches[i].distance)) {
              matches[j++] = matches[i];
          }
        }
        if (j == 0)
          break;
        matchlen++;
        nmatch = j;
      }

      /*
      * We've now got all the longest matches. We favour the
      * shorter distances, which means we go with matches[0].
      * So see if we want to defer it or throw it away.
      */
      matches[0].len = matchlen;
      if (defermatch.len > 0) {
        if (matches[0].len > defermatch.len + 1) {
          /* We have a better match. Emit the deferred char,
          * and defer this match. */
          ctx->literal(ctx, (unsigned char) deferchr);
          defermatch = matches[0];
          deferchr = data[0];
          advance = 1;
        } else {
          /* We don't have a better match. Do the deferred one. */
          ctx->match(ctx, defermatch.distance, defermatch.len);
          advance = defermatch.len - 1;
          defermatch.len = 0;
        }
      } else {
        /* There was no deferred match. Defer this one. */
        defermatch = matches[0];
        deferchr = data[0];
        advance = 1;
      }
    } else {
      /*
      * We found no matches. Emit the deferred match, if
      * any; otherwise emit a literal.
      */
      if (defermatch.len > 0) {
        ctx->match(ctx, defermatch.distance, defermatch.len);
        advance = defermatch.len - 1;
        defermatch.len = 0;
      } else {
        ctx->literal(ctx, data[0]);
        advance = 1;
      }
    }

    /*
    * Now advance the position by `advance' characters,
    * keeping the window and hash chains consistent.
    */
    while (advance > 0) {
      if (len >= HASHCHARS) {
        lz77_advance(st, *data, lz77_hash(data));
      } else {
        st->pending[st->npending++] = *data;
      }
      data++;
      len--;
      advance--;
    }
  }
}

/* ----------------------------------------------------------------------
* Deflate functionality common to both compression and decompression.
*/

static const unsigned char lenlenmap[] = {
  16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15
};

#define MAXCODELEN 16

/*
* Given a sequence of Huffman code lengths, compute the actual
* codes, in the final form suitable for feeding to outbits (i.e.
* already bit-mirrored).
*
* Returns the maximum code length found. Can also return -1 to
* indicate the table was overcommitted (too many or too short
* codes to exactly cover the possible space), or -2 to indicate it
* was undercommitted (too few or too long codes).
*/
static int hufcodes(const unsigned char *lengths, int *codes, int nsyms)
{
  int count[MAXCODELEN], startcode[MAXCODELEN];
  int code, maxlen;
  int i, j;

  /* Count the codes of each length. */
  maxlen = 0;
  for (i = 1; i < MAXCODELEN; i++)
    count[i] = 0;
  for (i = 0; i < nsyms; i++) {
    count[lengths[i]]++;
    if (maxlen < lengths[i])
      maxlen = lengths[i];
  }
  /* Determine the starting code for each length block. */
  code = 0;
  for (i = 1; i < MAXCODELEN; i++) {
    startcode[i] = code;
    code += count[i];
    if (code > (1 << i))
      maxlen = -1;	       /* overcommitted */
    code <<= 1;
  }
  if (code < (1 << MAXCODELEN))
    maxlen = -2;		       /* undercommitted */
  /* Determine the code for each symbol. Mirrored, of course. */
  for (i = 0; i < nsyms; i++) {
    code = startcode[lengths[i]]++;
    codes[i] = 0;
    for (j = 0; j < lengths[i]; j++) {
      codes[i] = (codes[i] << 1) | (code & 1);
      code >>= 1;
    }
  }

  return maxlen;
}

/*
* Adler32 checksum function.
*/
static unsigned long adler32_update(unsigned long s,
                                    const unsigned char *data, int len)
{
  unsigned s1 = s & 0xFFFF, s2 = (s >> 16) & 0xFFFF;
  int i;

  for (i = 0; i < len; i++) {
    s1 += data[i];
    s2 += s1;
    if (!(i & 0xFFF)) {
      s1 %= 65521;
      s2 %= 65521;
    }
  }

  return ((s2 % 65521) << 16) | (s1 % 65521);
}

/*
* CRC32 checksum function.
*/

static unsigned long crc32_update(unsigned long crcword,
                                  const unsigned char *data, int len)
{
  static const unsigned long crc32_table[256] = {
    0x00000000L, 0x77073096L, 0xEE0E612CL, 0x990951BAL,
    0x076DC419L, 0x706AF48FL, 0xE963A535L, 0x9E6495A3L,
    0x0EDB8832L, 0x79DCB8A4L, 0xE0D5E91EL, 0x97D2D988L,
    0x09B64C2BL, 0x7EB17CBDL, 0xE7B82D07L, 0x90BF1D91L,
    0x1DB71064L, 0x6AB020F2L, 0xF3B97148L, 0x84BE41DEL,
    0x1ADAD47DL, 0x6DDDE4EBL, 0xF4D4B551L, 0x83D385C7L,
    0x136C9856L, 0x646BA8C0L, 0xFD62F97AL, 0x8A65C9ECL,
    0x14015C4FL, 0x63066CD9L, 0xFA0F3D63L, 0x8D080DF5L,
    0x3B6E20C8L, 0x4C69105EL, 0xD56041E4L, 0xA2677172L,
    0x3C03E4D1L, 0x4B04D447L, 0xD20D85FDL, 0xA50AB56BL,
    0x35B5A8FAL, 0x42B2986CL, 0xDBBBC9D6L, 0xACBCF940L,
    0x32D86CE3L, 0x45DF5C75L, 0xDCD60DCFL, 0xABD13D59L,
    0x26D930ACL, 0x51DE003AL, 0xC8D75180L, 0xBFD06116L,
    0x21B4F4B5L, 0x56B3C423L, 0xCFBA9599L, 0xB8BDA50FL,
    0x2802B89EL, 0x5F058808L, 0xC60CD9B2L, 0xB10BE924L,
    0x2F6F7C87L, 0x58684C11L, 0xC1611DABL, 0xB6662D3DL,
    0x76DC4190L, 0x01DB7106L, 0x98D220BCL, 0xEFD5102AL,
    0x71B18589L, 0x06B6B51FL, 0x9FBFE4A5L, 0xE8B8D433L,
    0x7807C9A2L, 0x0F00F934L, 0x9609A88EL, 0xE10E9818L,
    0x7F6A0DBBL, 0x086D3D2DL, 0x91646C97L, 0xE6635C01L,
    0x6B6B51F4L, 0x1C6C6162L, 0x856530D8L, 0xF262004EL,
    0x6C0695EDL, 0x1B01A57BL, 0x8208F4C1L, 0xF50FC457L,
    0x65B0D9C6L, 0x12B7E950L, 0x8BBEB8EAL, 0xFCB9887CL,
    0x62DD1DDFL, 0x15DA2D49L, 0x8CD37CF3L, 0xFBD44C65L,
    0x4DB26158L, 0x3AB551CEL, 0xA3BC0074L, 0xD4BB30E2L,
    0x4ADFA541L, 0x3DD895D7L, 0xA4D1C46DL, 0xD3D6F4FBL,
    0x4369E96AL, 0x346ED9FCL, 0xAD678846L, 0xDA60B8D0L,
    0x44042D73L, 0x33031DE5L, 0xAA0A4C5FL, 0xDD0D7CC9L,
    0x5005713CL, 0x270241AAL, 0xBE0B1010L, 0xC90C2086L,
    0x5768B525L, 0x206F85B3L, 0xB966D409L, 0xCE61E49FL,
    0x5EDEF90EL, 0x29D9C998L, 0xB0D09822L, 0xC7D7A8B4L,
    0x59B33D17L, 0x2EB40D81L, 0xB7BD5C3BL, 0xC0BA6CADL,
    0xEDB88320L, 0x9ABFB3B6L, 0x03B6E20CL, 0x74B1D29AL,
    0xEAD54739L, 0x9DD277AFL, 0x04DB2615L, 0x73DC1683L,
    0xE3630B12L, 0x94643B84L, 0x0D6D6A3EL, 0x7A6A5AA8L,
    0xE40ECF0BL, 0x9309FF9DL, 0x0A00AE27L, 0x7D079EB1L,
    0xF00F9344L, 0x8708A3D2L, 0x1E01F268L, 0x6906C2FEL,
    0xF762575DL, 0x806567CBL, 0x196C3671L, 0x6E6B06E7L,
    0xFED41B76L, 0x89D32BE0L, 0x10DA7A5AL, 0x67DD4ACCL,
    0xF9B9DF6FL, 0x8EBEEFF9L, 0x17B7BE43L, 0x60B08ED5L,
    0xD6D6A3E8L, 0xA1D1937EL, 0x38D8C2C4L, 0x4FDFF252L,
    0xD1BB67F1L, 0xA6BC5767L, 0x3FB506DDL, 0x48B2364BL,
    0xD80D2BDAL, 0xAF0A1B4CL, 0x36034AF6L, 0x41047A60L,
    0xDF60EFC3L, 0xA867DF55L, 0x316E8EEFL, 0x4669BE79L,
    0xCB61B38CL, 0xBC66831AL, 0x256FD2A0L, 0x5268E236L,
    0xCC0C7795L, 0xBB0B4703L, 0x220216B9L, 0x5505262FL,
    0xC5BA3BBEL, 0xB2BD0B28L, 0x2BB45A92L, 0x5CB36A04L,
    0xC2D7FFA7L, 0xB5D0CF31L, 0x2CD99E8BL, 0x5BDEAE1DL,
    0x9B64C2B0L, 0xEC63F226L, 0x756AA39CL, 0x026D930AL,
    0x9C0906A9L, 0xEB0E363FL, 0x72076785L, 0x05005713L,
    0x95BF4A82L, 0xE2B87A14L, 0x7BB12BAEL, 0x0CB61B38L,
    0x92D28E9BL, 0xE5D5BE0DL, 0x7CDCEFB7L, 0x0BDBDF21L,
    0x86D3D2D4L, 0xF1D4E242L, 0x68DDB3F8L, 0x1FDA836EL,
    0x81BE16CDL, 0xF6B9265BL, 0x6FB077E1L, 0x18B74777L,
    0x88085AE6L, 0xFF0F6A70L, 0x66063BCAL, 0x11010B5CL,
    0x8F659EFFL, 0xF862AE69L, 0x616BFFD3L, 0x166CCF45L,
    0xA00AE278L, 0xD70DD2EEL, 0x4E048354L, 0x3903B3C2L,
    0xA7672661L, 0xD06016F7L, 0x4969474DL, 0x3E6E77DBL,
    0xAED16A4AL, 0xD9D65ADCL, 0x40DF0B66L, 0x37D83BF0L,
    0xA9BCAE53L, 0xDEBB9EC5L, 0x47B2CF7FL, 0x30B5FFE9L,
    0xBDBDF21CL, 0xCABAC28AL, 0x53B39330L, 0x24B4A3A6L,
    0xBAD03605L, 0xCDD70693L, 0x54DE5729L, 0x23D967BFL,
    0xB3667A2EL, 0xC4614AB8L, 0x5D681B02L, 0x2A6F2B94L,
    0xB40BBE37L, 0xC30C8EA1L, 0x5A05DF1BL, 0x2D02EF8DL
  };
  crcword ^= 0xFFFFFFFFL;
  while (len--) {
    unsigned long newbyte = *data++;
    newbyte ^= crcword & 0xFFL;
    crcword = (crcword >> 8) ^ crc32_table[newbyte];
  }
  return crcword ^ 0xFFFFFFFFL;
}

typedef struct {
  short code, extrabits;
  int min, max;
} coderecord;

static const coderecord lencodes[] = {
  {257, 0, 3, 3},
  {258, 0, 4, 4},
  {259, 0, 5, 5},
  {260, 0, 6, 6},
  {261, 0, 7, 7},
  {262, 0, 8, 8},
  {263, 0, 9, 9},
  {264, 0, 10, 10},
  {265, 1, 11, 12},
  {266, 1, 13, 14},
  {267, 1, 15, 16},
  {268, 1, 17, 18},
  {269, 2, 19, 22},
  {270, 2, 23, 26},
  {271, 2, 27, 30},
  {272, 2, 31, 34},
  {273, 3, 35, 42},
  {274, 3, 43, 50},
  {275, 3, 51, 58},
  {276, 3, 59, 66},
  {277, 4, 67, 82},
  {278, 4, 83, 98},
  {279, 4, 99, 114},
  {280, 4, 115, 130},
  {281, 5, 131, 162},
  {282, 5, 163, 194},
  {283, 5, 195, 226},
  {284, 5, 227, 257},
  {285, 0, 258, 258},
};

static const coderecord distcodes[] = {
  {0, 0, 1, 1},
  {1, 0, 2, 2},
  {2, 0, 3, 3},
  {3, 0, 4, 4},
  {4, 1, 5, 6},
  {5, 1, 7, 8},
  {6, 2, 9, 12},
  {7, 2, 13, 16},
  {8, 3, 17, 24},
  {9, 3, 25, 32},
  {10, 4, 33, 48},
  {11, 4, 49, 64},
  {12, 5, 65, 96},
  {13, 5, 97, 128},
  {14, 6, 129, 192},
  {15, 6, 193, 256},
  {16, 7, 257, 384},
  {17, 7, 385, 512},
  {18, 8, 513, 768},
  {19, 8, 769, 1024},
  {20, 9, 1025, 1536},
  {21, 9, 1537, 2048},
  {22, 10, 2049, 3072},
  {23, 10, 3073, 4096},
  {24, 11, 4097, 6144},
  {25, 11, 6145, 8192},
  {26, 12, 8193, 12288},
  {27, 12, 12289, 16384},
  {28, 13, 16385, 24576},
  {29, 13, 24577, 32768},
};

/* ----------------------------------------------------------------------
* Deflate compression.
*/

#define SYMLIMIT 65536
#define SYMPFX_LITLEN    0x00000000U
#define SYMPFX_DIST      0x40000000U
#define SYMPFX_EXTRABITS 0x80000000U
#define SYMPFX_CODELEN   0xC0000000U
#define SYMPFX_MASK      0xC0000000U

#define SYM_EXTRABITS_MASK 0x3C000000U
#define SYM_EXTRABITS_SHIFT 26

struct huftrees {
  unsigned char *len_litlen;
  int *code_litlen;
  unsigned char *len_dist;
  int *code_dist;
  unsigned char *len_codelen;
  int *code_codelen;
};

struct deflate_compress_ctx {
  struct LZ77Context *lzc;
  unsigned char *outbuf;
  int outlen, outsize;
  unsigned long outbits;
  int noutbits;
  int firstblock;
  unsigned long *syms;
  int symstart, nsyms;
  int type;
  unsigned long checksum;
  unsigned long datasize;
  int lastblock;
  int finished;
  unsigned char static_len1[288], static_len2[30];
  int static_code1[288], static_code2[30];
  struct huftrees sht;
#ifdef STATISTICS
  unsigned long bitcount;
#endif
};

static void outbits(deflate_compress_ctx *out,
                    unsigned long bits, int nbits)
{
  assert(out->noutbits + nbits <= 32);
  out->outbits |= bits << out->noutbits;
  out->noutbits += nbits;
  while (out->noutbits >= 8) {
    if (out->outlen >= out->outsize) {
      out->outsize = out->outlen + 64;
      out->outbuf = sresize(out->outbuf, out->outsize, unsigned char);
    }
    out->outbuf[out->outlen++] = (unsigned char) (out->outbits & 0xFF);
    out->outbits >>= 8;
    out->noutbits -= 8;
  }
#ifdef STATISTICS
  out->bitcount += nbits;
#endif
}

/*
* Binary heap functions used by buildhuf(). Each one assumes the
* heap to be stored in an array of ints, with two ints per node
* (user data and key). They take in the old heap length, and
* return the new one.
*/
#define HEAPPARENT(x) (((x)-2)/4*2)
#define HEAPLEFT(x) ((x)*2+2)
#define HEAPRIGHT(x) ((x)*2+4)
static int addheap(int *heap, int len, int userdata, int key)
{
  int me, dad, tmp;

  me = len;
  heap[len++] = userdata;
  heap[len++] = key;

  while (me > 0) {
    dad = HEAPPARENT(me);
    if (heap[me+1] < heap[dad+1]) {
      tmp = heap[me]; heap[me] = heap[dad]; heap[dad] = tmp;
      tmp = heap[me+1]; heap[me+1] = heap[dad+1]; heap[dad+1] = tmp;
      me = dad;
    } else
      break;
  }

  return len;
}
static int rmheap(int *heap, int len, int *userdata, int *key)
{
  int me, lc, rc, c, tmp;

  len -= 2;
  *userdata = heap[0];
  *key = heap[1];
  heap[0] = heap[len];
  heap[1] = heap[len+1];

  me = 0;

  while (1) {
    lc = HEAPLEFT(me);
    rc = HEAPRIGHT(me);
    if (lc >= len)
      break;
    else if (rc >= len || heap[lc+1] < heap[rc+1])
      c = lc;
    else
      c = rc;
    if (heap[me+1] > heap[c+1]) {
      tmp = heap[me]; heap[me] = heap[c]; heap[c] = tmp;
      tmp = heap[me+1]; heap[me+1] = heap[c+1]; heap[c+1] = tmp;
    } else
      break;
    me = c;
  }

  return len;
}

/*
* The core of the Huffman algorithm: takes an input array of
* symbol frequencies, and produces an output array of code
* lengths.
*
* This is basically a generic Huffman implementation, but it has
* one zlib-related quirk which is that it caps the output code
* lengths to fit in an unsigned char (which is safe since Deflate
* will reject anything longer than 15 anyway). Anyone wanting to
* rip it out and use it in another context should find that easy
* to remove.
*/
#define HUFMAX 286
static void buildhuf(const int *freqs, unsigned char *lengths, int nsyms)
{
  int parent[2*HUFMAX-1];
  int length[2*HUFMAX-1];
  int heap[2*HUFMAX];
  int heapsize;
  int i, j, n;
  int si, sj;

  assert(nsyms <= HUFMAX);

  memset(parent, 0, sizeof(parent));

  /*
  * Begin by building the heap.
  */
  heapsize = 0;
  for (i = 0; i < nsyms; i++)
    if (freqs[i] > 0)	       /* leave unused symbols out totally */
      heapsize = addheap(heap, heapsize, i, freqs[i]);

  /*
  * Now repeatedly take two elements off the heap and merge
  * them.
  */
  n = HUFMAX;
  while (heapsize > 2) {
    heapsize = rmheap(heap, heapsize, &i, &si);
    heapsize = rmheap(heap, heapsize, &j, &sj);
    parent[i] = n;
    parent[j] = n;
    heapsize = addheap(heap, heapsize, n, si + sj);
    n++;
  }

  /*
  * Now we have our tree, in the form of a link from each node
  * to the index of its parent. Count back down the tree to
  * determine the code lengths.
  */
  memset(length, 0, sizeof(length));
  /* The tree root has length 0 after that, which is correct. */
  for (i = n-1; i-- ;)
    if (parent[i] > 0)
      length[i] = 1 + length[parent[i]];

  /*
  * And that's it. (Simple, wasn't it?) Copy the lengths into
  * the output array and leave.
  * 
  * Here we cap lengths to fit in unsigned char.
  */
  for (i = 0; i < nsyms; i++)
    lengths[i] = (length[i] > 255 ? 255 : length[i]);
}

/*
* Wrapper around buildhuf() which enforces the Deflate restriction
* that no code length may exceed 15 bits, or 7 for the auxiliary
* code length alphabet. This function has the same calling
* semantics as buildhuf(), except that it might modify the freqs
* array.
*/
static void deflate_buildhuf(int *freqs, unsigned char *lengths,
                             int nsyms, int limit)
{
  int smallestfreq, totalfreq, nactivesyms;
  int num, denom, adjust;
  int i;
  int maxprob;

  /*
  * Nasty special case: if the frequency table has fewer than
  * two non-zero elements, we must invent some, because we can't
  * have fewer than one bit encoding a symbol.
  */
  assert(nsyms >= 2);
  {
    int count = 0;
    for (i = 0; i < nsyms; i++)
      if (freqs[i] > 0)
        count++;
    if (count < 2) {
      for (i = 0; i < nsyms && count > 0; i++)
        if (freqs[i] == 0) {
          freqs[i] = 1;
          count--;
        }
    }
  }

  /*
  * First, try building the Huffman table the normal way. If
  * this works, it's optimal, so we don't want to mess with it.
  */
  buildhuf(freqs, lengths, nsyms);

  for (i = 0; i < nsyms; i++)
    if (lengths[i] > limit)
      break;

  if (i == nsyms)
    return;			       /* OK */

  /*
  * The Huffman algorithm can only ever generate a code length
  * of N bits or more if there is a symbol whose probability is
  * less than the reciprocal of the (N+2)th Fibonacci number
  * (counting from F_0=0 and F_1=1), i.e. 1/2584 for N=16, or
  * 1/55 for N=8. (This is a necessary though not sufficient
  * condition.)
  *
  * Why is this? Well, consider the input symbol with the
  * smallest probability. Let that probability be x. In order
  * for this symbol to have a code length of at least 1, the
  * Huffman algorithm will have to merge it with some other
  * node; and since x is the smallest probability, the node it
  * gets merged with must be at least x. Thus, the probability
  * of the resulting combined node will be at least 2x. Now in
  * order for our node to reach depth 2, this 2x-node must be
  * merged again. But what with? We can't assume the node it
  * merges with is at least 2x, because this one might only be
  * the _second_ smallest remaining node. But we do know the
  * node it merges with must be at least x, so our order-2
  * internal node is at least 3x.
  *
  * How small a node can merge with _that_ to get an order-3
  * internal node? Well, it must be at least 2x, because if it
  * was smaller than that then it would have been one of the two
  * smallest nodes in the previous step and been merged at that
  * point. So at least 3x, plus at least 2x, comes to at least
  * 5x for an order-3 node.
  *
  * And so it goes on: at every stage we must merge our current
  * node with a node at least as big as the bigger of this one's
  * two parents, and from this starting point that gives rise to
  * the Fibonacci sequence. So we find that in order to have a
  * node n levels deep (i.e. a maximum code length of n), the
  * overall probability of the root of the entire tree must be
  * at least F_{n+2} times the probability of the rarest symbol.
  * In other words, since the overall probability is 1, it is a
  * necessary condition for a code length of 16 or more that
  * there must be at least one symbol with probability <=
  * 1/F_18.
  *
  * (To demonstrate that a probability this big really can give
  * rise to a code length of 16, consider the set of input
  * frequencies { 1-epsilon, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55,
  * 89, 144, 233, 377, 610, 987 }, for arbitrarily small
  * epsilon.)
  *
  * So here buildhuf() has returned us an overlong code. So to
  * ensure it doesn't do it again, we add a constant to all the
  * (non-zero) symbol frequencies, causing them to become more
  * balanced and removing the danger. We can then feed the
  * results back to the standard buildhuf() and be
  * assert()-level confident that the resulting code lengths
  * contain nothing outside the permitted range.
  */
  assert(limit == 15 || limit == 7);
  maxprob = (limit == 15 ? 2584 : 55);   /* no point in computing full F_n */
  totalfreq = nactivesyms = 0;
  smallestfreq = -1;
  for (i = 0; i < nsyms; i++) {
    if (freqs[i] == 0)
      continue;
    if (smallestfreq < 0 || smallestfreq > freqs[i])
      smallestfreq = freqs[i];
    totalfreq += freqs[i];
    nactivesyms++;
  }
  assert(smallestfreq <= totalfreq / maxprob);

  /*
  * We want to find the smallest integer `adjust' such that
  * (totalfreq + nactivesyms * adjust) / (smallestfreq +
  * adjust) is less than maxprob. A bit of algebra tells us
  * that the threshold value is equal to
  *
  *   totalfreq - maxprob * smallestfreq
  *   ----------------------------------
  *          maxprob - nactivesyms
  *
  * rounded up, of course. And we'll only even be trying
  * this if
  */
  num = totalfreq - smallestfreq * maxprob;
  denom = maxprob - nactivesyms;
  adjust = (num + denom - 1) / denom;

  /*
  * Now add `adjust' to all the input symbol frequencies.
  */
  for (i = 0; i < nsyms; i++)
    if (freqs[i] != 0)
      freqs[i] += adjust;

  /*
  * Rebuild the Huffman tree...
  */
  buildhuf(freqs, lengths, nsyms);

  /*
  * ... and this time it ought to be OK.
  */
  for (i = 0; i < nsyms; i++)
    assert(lengths[i] <= limit);
}

/*
* Compute the bit length of a symbol, given the three Huffman
* trees.
*/
static int symsize(unsigned sym, const struct huftrees *trees)
{
  unsigned basesym = sym &~ SYMPFX_MASK;

  switch (sym & SYMPFX_MASK) {
case SYMPFX_LITLEN:
  return trees->len_litlen[basesym];
case SYMPFX_DIST:
  return trees->len_dist[basesym];
case SYMPFX_CODELEN:
  return trees->len_codelen[basesym];
default /*case SYMPFX_EXTRABITS*/:
  return basesym >> SYM_EXTRABITS_SHIFT;
  }
}

/*
* Write out a single symbol, given the three Huffman trees.
*/
static void writesym(deflate_compress_ctx *out,
                     unsigned sym, const struct huftrees *trees)
{
  unsigned basesym = sym &~ SYMPFX_MASK;
  int i;

  switch (sym & SYMPFX_MASK) {
case SYMPFX_LITLEN:
  debug(("send: litlen %d\n", basesym));
  outbits(out, trees->code_litlen[basesym], trees->len_litlen[basesym]);
  break;
case SYMPFX_DIST:
  debug(("send: dist %d\n", basesym));
  outbits(out, trees->code_dist[basesym], trees->len_dist[basesym]);
  break;
case SYMPFX_CODELEN:
  debug(("send: codelen %d\n", basesym));
  outbits(out, trees->code_codelen[basesym],trees->len_codelen[basesym]);
  break;
case SYMPFX_EXTRABITS:
  i = basesym >> SYM_EXTRABITS_SHIFT;
  basesym &= ~SYM_EXTRABITS_MASK;
  debug(("send: extrabits %d/%d\n", basesym, i));
  outbits(out, basesym, i);
  break;
  }
}

/*
* outblock() must output _either_ a dynamic block of length
* `dynamic_len', _or_ a static block of length `static_len', but
* it gets to choose which.
*/
static void outblock(deflate_compress_ctx *out,
                     int dynamic_len, int static_len)
{
  int freqs1[286], freqs2[30], freqs3[19];
  unsigned char len1[286], len2[30], len3[19];
  int code1[286], code2[30], code3[19];
  int hlit, hdist, hclen, bfinal, btype;
  int treesrc[286 + 30];
  int treesyms[286 + 30];
  int codelen[19];
  int i, ntreesrc, ntreesyms;
  int dynamic, blklen;
  struct huftrees dht;
  const struct huftrees *ht;
#ifdef STATISTICS
  unsigned long bitcount_before;
#endif

  dht.len_litlen = len1;
  dht.len_dist = len2;
  dht.len_codelen = len3;
  dht.code_litlen = code1;
  dht.code_dist = code2;
  dht.code_codelen = code3;

  /*
  * We make our choice of block to output by doing all the
  * detailed work to determine the exact length of each possible
  * block. Then we choose the one which has fewest output bits
  * per symbol.
  */

  /*
  * First build the two main Huffman trees for the dynamic
  * block.
  */

  /*
  * Count up the frequency tables.
  */
  memset(freqs1, 0, sizeof(freqs1));
  memset(freqs2, 0, sizeof(freqs2));
  freqs1[256] = 1;	       /* we're bound to need one EOB */
  for (i = 0; i < dynamic_len; i++) {
    unsigned sym = out->syms[(out->symstart + i) % SYMLIMIT];

    /*
    * Increment the occurrence counter for this symbol, if
    * it's in one of the Huffman alphabets and isn't extra
    * bits.
    */
    if ((sym & SYMPFX_MASK) == SYMPFX_LITLEN) {
      sym &= ~SYMPFX_MASK;
      assert(sym < lenof(freqs1));
      freqs1[sym]++;
    } else if ((sym & SYMPFX_MASK) == SYMPFX_DIST) {
      sym &= ~SYMPFX_MASK;
      assert(sym < lenof(freqs2));
      freqs2[sym]++;
    }
  }
  deflate_buildhuf(freqs1, len1, lenof(freqs1), 15);
  deflate_buildhuf(freqs2, len2, lenof(freqs2), 15);
  hufcodes(len1, code1, lenof(freqs1));
  hufcodes(len2, code2, lenof(freqs2));

  /*
  * Determine HLIT and HDIST.
  */
  for (hlit = 286; hlit > 257 && len1[hlit-1] == 0; hlit--);
  for (hdist = 30; hdist > 1 && len2[hdist-1] == 0; hdist--);

  /*
  * Write out the list of symbols used to transmit the
  * trees.
  */
  ntreesrc = 0;
  for (i = 0; i < hlit; i++)
    treesrc[ntreesrc++] = len1[i];
  for (i = 0; i < hdist; i++)
    treesrc[ntreesrc++] = len2[i];
  ntreesyms = 0;
  for (i = 0; i < ntreesrc ;) {
    int j = 1;
    int k;

    /* Find length of run of the same length code. */
    while (i+j < ntreesrc && treesrc[i+j] == treesrc[i])
      j++;

    /* Encode that run as economically as we can. */
    k = j;
    if (treesrc[i] == 0) {
      /*
      * Zero code length: we can output run codes for
      * 3-138 zeroes. So if we have fewer than 3 zeroes,
      * we just output literals. Otherwise, we output
      * nothing but run codes, and tweak their lengths
      * to make sure we aren't left with under 3 at the
      * end.
      */
      if (k < 3) {
        while (k--)
          treesyms[ntreesyms++] = 0 | SYMPFX_CODELEN;
      } else {
        while (k > 0) {
          int rpt = (k < 138 ? k : 138);
          if (rpt > k-3 && rpt < k)
            rpt = k-3;
          assert(rpt >= 3 && rpt <= 138);
          if (rpt < 11) {
            treesyms[ntreesyms++] = 17 | SYMPFX_CODELEN;
            treesyms[ntreesyms++] =
              (SYMPFX_EXTRABITS | (rpt - 3) |
              (3 << SYM_EXTRABITS_SHIFT));
          } else {
            treesyms[ntreesyms++] = 18 | SYMPFX_CODELEN;
            treesyms[ntreesyms++] =
              (SYMPFX_EXTRABITS | (rpt - 11) |
              (7 << SYM_EXTRABITS_SHIFT));
          }
          k -= rpt;
        }
      }
    } else {
      /*
      * Non-zero code length: we must output the first
      * one explicitly, then we can output a copy code
      * for 3-6 repeats. So if we have fewer than 4
      * repeats, we _just_ output literals. Otherwise,
      * we output one literal plus at least one copy
      * code, and tweak the copy codes to make sure we
      * aren't left with under 3 at the end.
      */
      assert(treesrc[i] < 16);
      treesyms[ntreesyms++] = treesrc[i] | SYMPFX_CODELEN;
      k--;
      if (k < 3) {
        while (k--)
          treesyms[ntreesyms++] = treesrc[i] | SYMPFX_CODELEN;
      } else {
        while (k > 0) {
          int rpt = (k < 6 ? k : 6);
          if (rpt > k-3 && rpt < k)
            rpt = k-3;
          assert(rpt >= 3 && rpt <= 6);
          treesyms[ntreesyms++] = 16 | SYMPFX_CODELEN;
          treesyms[ntreesyms++] = (SYMPFX_EXTRABITS | (rpt - 3) |
            (2 << SYM_EXTRABITS_SHIFT));
          k -= rpt;
        }
      }
    }

    i += j;
  }
  assert((unsigned)ntreesyms < lenof(treesyms));

  /*
  * Count up the frequency table for the tree-transmission
  * symbols, and build the auxiliary Huffman tree for that.
  */
  memset(freqs3, 0, sizeof(freqs3));
  for (i = 0; i < ntreesyms; i++) {
    unsigned sym = treesyms[i];

    /*
    * Increment the occurrence counter for this symbol, if
    * it's the Huffman alphabet and isn't extra bits.
    */
    if ((sym & SYMPFX_MASK) == SYMPFX_CODELEN) {
      sym &= ~SYMPFX_MASK;
      assert(sym < lenof(freqs3));
      freqs3[sym]++;
    }
  }
  deflate_buildhuf(freqs3, len3, lenof(freqs3), 7);
  hufcodes(len3, code3, lenof(freqs3));

  /*
  * Reorder the code length codes into transmission order, and
  * determine HCLEN.
  */
  for (i = 0; i < 19; i++)
    codelen[i] = len3[lenlenmap[i]];
  for (hclen = 19; hclen > 4 && codelen[hclen-1] == 0; hclen--);

  /*
  * Now work out the exact size of both the dynamic and the
  * static block, in bits.
  */
  {
    int ssize, dsize;

    /*
    * First the dynamic block.
    */
    dsize = 3 + 5 + 5 + 4;	       /* 3-bit header, HLIT, HDIST, HCLEN */
    dsize += 3 * hclen;	       /* code-length-alphabet code lengths */
    /* Code lengths */
    for (i = 0; i < ntreesyms; i++)
      dsize += symsize(treesyms[i], &dht);
    /* The actual block data */
    for (i = 0; i < dynamic_len; i++) {
      unsigned sym = out->syms[(out->symstart + i) % SYMLIMIT];
      dsize += symsize(sym, &dht);
    }
    /* And the end-of-data symbol. */
    dsize += symsize(SYMPFX_LITLEN | 256, &dht);

    /*
    * Now the static block.
    */
    ssize = 3;		       /* 3-bit block header */
    /* The actual block data */
    for (i = 0; i < static_len; i++) {
      unsigned sym = out->syms[(out->symstart + i) % SYMLIMIT];
      ssize += symsize(sym, &out->sht);
    }
    /* And the end-of-data symbol. */
    ssize += symsize(SYMPFX_LITLEN | 256, &out->sht);

    /*
    * Compare the two and decide which to output. We break
    * exact ties in favour of the static block, because of the
    * special case in which that block has zero length.
    */
    dynamic = ((double)ssize * dynamic_len > (double)dsize * static_len);
    ht = dynamic ? &dht : &out->sht;
    blklen = dynamic ? dynamic_len : static_len;
  }

  /*
  * Actually transmit the block.
  */

  /* 3-bit block header */
  bfinal = (out->lastblock ? 1 : 0);
  btype = dynamic ? 2 : 1;
  debug(("send: bfinal=%d btype=%d\n", bfinal, btype));
  outbits(out, bfinal, 1);
  outbits(out, btype, 2);

#ifdef STATISTICS
  bitcount_before = out->bitcount;
#endif

  if (dynamic) {
    /* HLIT, HDIST and HCLEN */
    debug(("send: hlit=%d hdist=%d hclen=%d\n", hlit, hdist, hclen));
    outbits(out, hlit - 257, 5);
    outbits(out, hdist - 1, 5);
    outbits(out, hclen - 4, 4);

    /* Code lengths for the auxiliary tree */
    for (i = 0; i < hclen; i++) {
      debug(("send: lenlen %d\n", codelen[i]));
      outbits(out, codelen[i], 3);
    }

    /* Code lengths for the literal/length and distance trees */
    for (i = 0; i < ntreesyms; i++)
      writesym(out, treesyms[i], ht);
#ifdef STATISTICS
    fprintf(stderr, "total tree size %lu bits\n",
      out->bitcount - bitcount_before);
#endif
  }

  /* Output the actual symbols from the buffer */
  for (i = 0; i < blklen; i++) {
    unsigned sym = out->syms[(out->symstart + i) % SYMLIMIT];
    writesym(out, sym, ht);
  }

  /* Output the end-of-data symbol */
  writesym(out, SYMPFX_LITLEN | 256, ht);

  /*
  * Remove all the just-output symbols from the symbol buffer by
  * adjusting symstart and nsyms.
  */
  out->symstart = (out->symstart + blklen) % SYMLIMIT;
  out->nsyms -= blklen;
}

/*
* Give the approximate log-base-2 of an input integer, measured in
* 8ths of a bit. (I.e. this computes an integer approximation to
* 8*logbase2(x).)
*/
static int approxlog2(unsigned x)
{
  int ret = 31*8;

  /*
  * Binary-search to get the top bit of x up to bit 31.
  */
  if (x < 0x00010000U) x <<= 16, ret -= 16*8;
  if (x < 0x01000000U) x <<=  8, ret -=  8*8;
  if (x < 0x10000000U) x <<=  4, ret -=  4*8;
  if (x < 0x40000000U) x <<=  2, ret -=  2*8;
  if (x < 0x80000000U) x <<=  1, ret -=  1*8;

  /*
  * Now we know the logarithm we want is in [ret,ret+1).
  * Determine the bottom three bits by checking against
  * threshold values.
  * 
  * (Each of these threshold values is 0x80000000 times an odd
  * power of 2^(1/16). Therefore, this function rounds to
  * nearest.)
  */
  if (x <= 0xAD583EEAU) {
    if (x <= 0x91C3D373U)
      ret += (x <= 0x85AAC367U ? 0 : 1);
    else
      ret += (x <= 0x9EF53260U ? 2 : 3);
  } else {
    if (x <= 0xCE248C15U)
      ret += (x <= 0xBD08A39FU ? 4 : 5);
    else
      ret += (x <= 0xE0CCDEECU ? 6 : x <= 0xF5257D15L ? 7 : 8);
  }

  return ret;
}

static void chooseblock(deflate_compress_ctx *out)
{
  int freqs1[286], freqs2[30];
  int i, len, bestlen, longestlen = 0;
  int total1, total2;
  int bestvfm;

  memset(freqs1, 0, sizeof(freqs1));
  memset(freqs2, 0, sizeof(freqs2));
  freqs1[256] = 1;		       /* we're bound to need one EOB */
  total1 = 1;
  total2 = 0;

  /*
  * Iterate over all possible block lengths, computing the
  * entropic coding approximation to the final length at every
  * stage. We divide the result by the number of symbols
  * encoded, to determine the `value for money' (overall
  * bits-per-symbol count) of a block of that length.
  */
  bestlen = -1;
  bestvfm = 0;

  len = 300 * 8;	      /* very approximate size of the Huffman trees */

  for (i = 0; i < out->nsyms; i++) {
    unsigned sym = out->syms[(out->symstart + i) % SYMLIMIT];

    if (i > 0 && (sym & SYMPFX_MASK) == SYMPFX_LITLEN) {
      /*
      * This is a viable point at which to end the block.
      * Compute the value for money.
      */
      int vfm = i * 32768 / len;      /* symbols encoded per bit */

      if (bestlen < 0 || vfm > bestvfm) {
        bestlen = i;
        bestvfm = vfm;
      }

      longestlen = i;
    }

    /*
    * Increment the occurrence counter for this symbol, if
    * it's in one of the Huffman alphabets and isn't extra
    * bits.
    */
    if ((sym & SYMPFX_MASK) == SYMPFX_LITLEN) {
      sym &= ~SYMPFX_MASK;
      assert(sym < lenof(freqs1));
      len += freqs1[sym] * approxlog2(freqs1[sym]);
      len -= total1 * approxlog2(total1);
      freqs1[sym]++;
      total1++;
      len -= freqs1[sym] * approxlog2(freqs1[sym]);
      len += total1 * approxlog2(total1);
    } else if ((sym & SYMPFX_MASK) == SYMPFX_DIST) {
      sym &= ~SYMPFX_MASK;
      assert(sym < lenof(freqs2));
      len += freqs2[sym] * approxlog2(freqs2[sym]);
      len -= total2 * approxlog2(total2);
      freqs2[sym]++;
      total2++;
      len -= freqs2[sym] * approxlog2(freqs2[sym]);
      len += total2 * approxlog2(total2);
    } else if ((sym & SYMPFX_MASK) == SYMPFX_EXTRABITS) {
      len += 8 * ((sym &~ SYMPFX_MASK) >> SYM_EXTRABITS_SHIFT);
    }
  }

  assert(bestlen > 0);

  outblock(out, bestlen, longestlen);
}

/*
* Force the current symbol buffer to be flushed out as a single
* block.
*/
static void flushblock(deflate_compress_ctx *out)
{
  /*
  * No need to check that out->nsyms is a valid block length: we
  * know it has to be, because flushblock() is called in between
  * two matches/literals.
  */
  outblock(out, out->nsyms, out->nsyms);
  assert(out->nsyms == 0);
}

/*
* Place a symbol into the symbols buffer.
*/
static void outsym(deflate_compress_ctx *out, unsigned long sym)
{
  assert(out->nsyms < SYMLIMIT);
  out->syms[(out->symstart + out->nsyms++) % SYMLIMIT] = sym;

  if (out->nsyms == SYMLIMIT)
    chooseblock(out);
}

static void literal(struct LZ77Context *ectx, unsigned char c)
{
  deflate_compress_ctx *out = (deflate_compress_ctx *) ectx->userdata;

  outsym(out, SYMPFX_LITLEN | c);
}

static void match(struct LZ77Context *ectx, int distance, int len)
{
  const coderecord *d, *l;
  int i, j, k;
  deflate_compress_ctx *out = (deflate_compress_ctx *) ectx->userdata;

  while (len > 0) {
    int thislen;

    /*
    * We can transmit matches of lengths 3 through 258
    * inclusive. So if len exceeds 258, we must transmit in
    * several steps, with 258 or less in each step.
    *
    * Specifically: if len >= 261, we can transmit 258 and be
    * sure of having at least 3 left for the next step. And if
    * len <= 258, we can just transmit len. But if len == 259
    * or 260, we must transmit len-3.
    */
    thislen = (len > 260 ? 258 : len <= 258 ? len : len - 3);
    len -= thislen;

    /*
    * Binary-search to find which length code we're
    * transmitting.
    */
    i = -1;
    j = sizeof(lencodes) / sizeof(*lencodes);
    while (1) {
      assert(j - i >= 2);
      k = (j + i) / 2;
      if (thislen < lencodes[k].min)
        j = k;
      else if (thislen > lencodes[k].max)
        i = k;
      else {
        l = &lencodes[k];
        break;                 /* found it! */
      }
    }

    /*
    * Transmit the length code.
    */
    outsym(out, SYMPFX_LITLEN | l->code);

    /*
    * Transmit the extra bits.
    */
    if (l->extrabits) {
      outsym(out, (SYMPFX_EXTRABITS | (thislen - l->min) |
        (l->extrabits << SYM_EXTRABITS_SHIFT)));
    }

    /*
    * Binary-search to find which distance code we're
    * transmitting.
    */
    i = -1;
    j = sizeof(distcodes) / sizeof(*distcodes);
    while (1) {
      assert(j - i >= 2);
      k = (j + i) / 2;
      if (distance < distcodes[k].min)
        j = k;
      else if (distance > distcodes[k].max)
        i = k;
      else {
        d = &distcodes[k];
        break;                 /* found it! */
      }
    }

    /*
    * Write the distance code.
    */
    outsym(out, SYMPFX_DIST | d->code);

    /*
    * Transmit the extra bits.
    */
    if (d->extrabits) {
      outsym(out, (SYMPFX_EXTRABITS | (distance - d->min) |
        (d->extrabits << SYM_EXTRABITS_SHIFT)));
    }
  }
}

deflate_compress_ctx *deflate_compress_new(int type)
{
  deflate_compress_ctx *out;
  struct LZ77Context *ectx = snew(struct LZ77Context);

  lz77_init(ectx);
  ectx->literal = literal;
  ectx->match = match;

  out = snew(deflate_compress_ctx);
  out->type = type;
  out->outbits = out->noutbits = 0;
  out->firstblock = TRUE;
#ifdef STATISTICS
  out->bitcount = 0;
#endif

  out->syms = snewn(SYMLIMIT, unsigned long);
  out->symstart = out->nsyms = 0;

  out->checksum = (type == DEFLATE_TYPE_ZLIB ? 1 : 0);
  out->datasize = 0;
  out->lastblock = FALSE;
  out->finished = FALSE;

  /*
  * Build the static Huffman tables now, so we'll have them
  * available every time outblock() is called.
  */
  {
    int i;

    for (i = 0; i < (int)lenof(out->static_len1); i++)
      out->static_len1[i] = (i < 144 ? 8 :
      i < 256 ? 9 :
      i < 280 ? 7 : 8);
    for (i = 0; i < (int)lenof(out->static_len2); i++)
      out->static_len2[i] = 5;
  }
  hufcodes(out->static_len1, out->static_code1, lenof(out->static_code1));
  hufcodes(out->static_len2, out->static_code2, lenof(out->static_code2));
  out->sht.len_litlen = out->static_len1;
  out->sht.len_dist = out->static_len2;
  out->sht.len_codelen = NULL;
  out->sht.code_litlen = out->static_code1;
  out->sht.code_dist = out->static_code2;
  out->sht.code_codelen = NULL;

  ectx->userdata = out;
  out->lzc = ectx;

  return out;
}

void deflate_compress_free(deflate_compress_ctx *out)
{
  struct LZ77Context *ectx = out->lzc;

  sfree(out->syms);
  sfree(ectx->ictx);
  sfree(ectx);
  sfree(out);
}

void deflate_compress_data(deflate_compress_ctx *out,
                           const void *vblock, int len, int flushtype,
                           void **outblock, int *outlen)
{
  struct LZ77Context *ectx = out->lzc;
  const unsigned char *block = (const unsigned char *)vblock;

  assert(!out->finished);

  out->outbuf = NULL;
  out->outlen = out->outsize = 0;

  /*
  * If this is the first block, output the header.
  */
  if (out->firstblock) {
    switch (out->type) {
case DEFLATE_TYPE_BARE:
  break;		       /* no header */
case DEFLATE_TYPE_ZLIB:
  /*
  * zlib (RFC1950) header bytes: 78 9C. (Deflate
  * compression, 32K window size, default algorithm.)
  */
  outbits(out, 0x9C78, 16);
  break;
case DEFLATE_TYPE_GZIP:
  /*
  * Minimal gzip (RFC1952) header:
  * 
  *  - basic header of 1F 8B
  *  - compression method byte (8 = deflate)
  *  - flags byte (zero: we use no optional features)
  *  - modification time (zero: no time stamp available)
  * 	- extra flags byte (2: we use maximum compression
  * 	  always)
  *  - operating system byte (255: we do not specify)
  */
  outbits(out, 0x00088B1F, 32);   /* header, CM, flags */
  outbits(out, 0, 32);       /* mtime */
  outbits(out, 0xFF02, 16);  /* xflags, OS */
  break;
    }
    out->firstblock = FALSE;
  }

  /*
  * Feed our data to the LZ77 compression phase.
  */
  lz77_compress(ectx, block, len, TRUE);

  /*
  * Update checksums and counters.
  */
  switch (out->type) {
case DEFLATE_TYPE_ZLIB:
  out->checksum = adler32_update(out->checksum, block, len);
  break;
case DEFLATE_TYPE_GZIP:
  out->checksum = crc32_update(out->checksum, block, len);
  break;
  }
  out->datasize += len;

  switch (flushtype) {
    /*
    * FIXME: what other flush types are available and useful?
    * In PuTTY, it was clear that we generally wanted to be in
    * a static block so it was safe to open one. Here, we
    * probably prefer to be _outside_ a block if we can. Think
    * about this.
    */
case DEFLATE_NO_FLUSH:
  break;			       /* don't flush any data at all (duh) */
case DEFLATE_SYNC_FLUSH:
  /*
  * Close the current block.
  */
  flushblock(out);

  /*
  * Then output an empty _uncompressed_ block: send 000,
  * then sync to byte boundary, then send bytes 00 00 FF
  * FF.
  */
  outbits(out, 0, 3);
  if (out->noutbits)
    outbits(out, 0, 8 - out->noutbits);
  outbits(out, 0, 16);
  outbits(out, 0xFFFF, 16);
  break;
case DEFLATE_END_OF_DATA:
  /*
  * Output a block with BFINAL set.
  */
  out->lastblock = TRUE;
  flushblock(out);

  /*
  * Sync to byte boundary, flushing out the final byte.
  */
  if (out->noutbits)
    outbits(out, 0, 8 - out->noutbits);

  /*
  * Format-specific trailer data.
  */
  switch (out->type) {
case DEFLATE_TYPE_ZLIB:
  /*
  * Just write out the Adler32 checksum.
  */
  outbits(out, (out->checksum >> 24) & 0xFF, 8);
  outbits(out, (out->checksum >> 16) & 0xFF, 8);
  outbits(out, (out->checksum >>  8) & 0xFF, 8);
  outbits(out, (out->checksum >>  0) & 0xFF, 8);
  break;
case DEFLATE_TYPE_GZIP:
  /*
  * Write out the CRC32 checksum and the data length.
  */
  outbits(out, out->checksum, 32);
  outbits(out, out->datasize, 32);
  break;
  }

  out->finished = TRUE;
  break;
  }

  /*
  * Return any data that we've generated.
  */
  *outblock = (void *)out->outbuf;
  *outlen = out->outlen;
}

/* ----------------------------------------------------------------------
* Deflate decompression.
*/

/*
* The way we work the Huffman decode is to have a table lookup on
* the first N bits of the input stream (in the order they arrive,
* of course, i.e. the first bit of the Huffman code is in bit 0).
* Each table entry lists the number of bits to consume, plus
* either an output code or a pointer to a secondary table.
*/
struct table;
struct tableentry;

struct tableentry {
  unsigned char nbits;
  short code;
  struct table *nexttable;
};

struct table {
  int mask;			       /* mask applied to input bit stream */
  struct tableentry *table;
};

#define MAXSYMS 288

#define DWINSIZE 32768

/*
* Build a single-level decode table for elements
* [minlength,maxlength) of the provided code/length tables, and
* recurse to build subtables.
*/
static struct table *mkonetab(int *codes, unsigned char *lengths, int nsyms,
                              int pfx, int pfxbits, int bits)
{
  struct table *tab = snew(struct table);
  int pfxmask = (1 << pfxbits) - 1;
  int nbits, i, j, code;

  tab->table = snewn(1 << bits, struct tableentry);
  tab->mask = (1 << bits) - 1;

  for (code = 0; code <= tab->mask; code++) {
    tab->table[code].code = -1;
    tab->table[code].nbits = 0;
    tab->table[code].nexttable = NULL;
  }

  for (i = 0; i < nsyms; i++) {
    if (lengths[i] <= pfxbits || (codes[i] & pfxmask) != pfx)
      continue;
    code = (codes[i] >> pfxbits) & tab->mask;
    for (j = code; j <= tab->mask; j += 1 << (lengths[i] - pfxbits)) {
      tab->table[j].code = i;
      nbits = lengths[i] - pfxbits;
      if (tab->table[j].nbits < nbits)
        tab->table[j].nbits = nbits;
    }
  }
  for (code = 0; code <= tab->mask; code++) {
    if (tab->table[code].nbits <= bits)
      continue;
    /* Generate a subtable. */
    tab->table[code].code = -1;
    nbits = tab->table[code].nbits - bits;
    if (nbits > 7)
      nbits = 7;
    tab->table[code].nbits = bits;
    tab->table[code].nexttable = mkonetab(codes, lengths, nsyms,
      pfx | (code << pfxbits),
      pfxbits + bits, nbits);
  }

  return tab;
}

/*
* Build a decode table, given a set of Huffman tree lengths.
*/
static struct table *mktable(unsigned char *lengths, int nlengths,
#ifdef ANALYSIS
                             const char *alphabet,
#endif
                             int *error)
{
  int codes[MAXSYMS];
  int maxlen;

#ifdef ANALYSIS
  if (alphabet && analyse_level > 1) {
    int i, col = 0;
    printf("code lengths for %s alphabet:\n", alphabet);
    for (i = 0; i < nlengths; i++) {
      col += printf("%3d", lengths[i]);
      if (col > 72) {
        putchar('\n');
        col = 0;
      }
    }
    if (col > 0)
      putchar('\n');
  }
#endif

  maxlen = hufcodes(lengths, codes, nlengths);

  if (maxlen < 0) {
    *error = (maxlen == -1 ? DEFLATE_ERR_LARGE_HUFTABLE :
      DEFLATE_ERR_SMALL_HUFTABLE);
    return NULL;
  }

  /*
  * Now we have the complete list of Huffman codes. Build a
  * table.
  */
  return mkonetab(codes, lengths, nlengths, 0, 0, maxlen < 9 ? maxlen : 9);
}

static int freetable(struct table **ztab)
{
  struct table *tab;
  int code;

  if (ztab == NULL)
    return -1;

  if (*ztab == NULL)
    return 0;

  tab = *ztab;

  for (code = 0; code <= tab->mask; code++)
    if (tab->table[code].nexttable != NULL)
      freetable(&tab->table[code].nexttable);

  sfree(tab->table);
  tab->table = NULL;

  sfree(tab);
  *ztab = NULL;

  return (0);
}

struct deflate_decompress_ctx {
  struct table *staticlentable, *staticdisttable;
  struct table *currlentable, *currdisttable, *lenlentable;
  enum {
    ZLIBSTART,
    GZIPSTART, GZIPMETHFLAGS, GZIPIGNORE1, GZIPIGNORE2, GZIPIGNORE3,
    GZIPEXTRA, GZIPFNAME, GZIPCOMMENT,
    OUTSIDEBLK, TREES_HDR, TREES_LENLEN, TREES_LEN, TREES_LENREP,
    INBLK, GOTLENSYM, GOTLEN, GOTDISTSYM,
    UNCOMP_LEN, UNCOMP_NLEN, UNCOMP_DATA,
    END,
    ADLER1, ADLER2,
    CRC1, CRC2, ILEN1, ILEN2,
    FINALSPIN
  } state;
  int sym, hlit, hdist, hclen, lenptr, lenextrabits, lenaddon, len,
    lenrep, lastblock;
  int uncomplen;
  unsigned char lenlen[19];
  unsigned char lengths[286 + 32];
  unsigned long bits;
  int nbits;
  unsigned char window[DWINSIZE];
  int winpos;
  unsigned char *outblk;
  int outlen, outsize;
  int type;
  unsigned long checksum;
  unsigned long bytesout;
  int gzflags, gzextralen;
#ifdef ANALYSIS
  int bytesread;
  int bitcount_before;
#define BITCOUNT(dctx) ( (dctx)->bytesread * 8 - (dctx)->nbits )
#endif
};

deflate_decompress_ctx *deflate_decompress_new(int type)
{
  deflate_decompress_ctx *dctx = snew(deflate_decompress_ctx);
  unsigned char lengths[288];

  memset(lengths, 8, 144);
  memset(lengths + 144, 9, 256 - 144);
  memset(lengths + 256, 7, 280 - 256);
  memset(lengths + 280, 8, 288 - 280);
  dctx->staticlentable = mktable(lengths, 288,
#ifdef ANALYSIS
    NULL,
#endif
    NULL);
  assert(dctx->staticlentable);
  memset(lengths, 5, 32);
  dctx->staticdisttable = mktable(lengths, 32,
#ifdef ANALYSIS
    NULL,
#endif
    NULL);
  assert(dctx->staticdisttable);
  dctx->state = (type == DEFLATE_TYPE_ZLIB ? ZLIBSTART :
    type == DEFLATE_TYPE_GZIP ? GZIPSTART :
    OUTSIDEBLK);
  dctx->currlentable = dctx->currdisttable = dctx->lenlentable = NULL;
  dctx->bits = 0;
  dctx->nbits = 0;
  dctx->winpos = 0;
  dctx->type = type;
  dctx->lastblock = FALSE;
  dctx->checksum = (type == DEFLATE_TYPE_ZLIB ? 1 : 0);
  dctx->bytesout = 0;
  dctx->gzflags = dctx->gzextralen = 0;
#ifdef ANALYSIS
  dctx->bytesread = dctx->bitcount_before = 0;
#endif

  return dctx;
}

void deflate_decompress_free(deflate_decompress_ctx *dctx)
{
  if (dctx->currlentable && dctx->currlentable != dctx->staticlentable)
    freetable(&dctx->currlentable);
  if (dctx->currdisttable && dctx->currdisttable != dctx->staticdisttable)
    freetable(&dctx->currdisttable);
  if (dctx->lenlentable)
    freetable(&dctx->lenlentable);
  freetable(&dctx->staticlentable);
  freetable(&dctx->staticdisttable);
  sfree(dctx);
}

static int huflookup(unsigned long *bitsp, int *nbitsp, struct table *tab)
{
  unsigned long bits = *bitsp;
  int nbits = *nbitsp;
  while (1) {
    struct tableentry *ent;
    ent = &tab->table[bits & tab->mask];
    if (ent->nbits > nbits)
      return -1;		       /* not enough data */
    bits >>= ent->nbits;
    nbits -= ent->nbits;
    if (ent->code == -1)
      tab = ent->nexttable;
    else {
      *bitsp = bits;
      *nbitsp = nbits;
      return ent->code;
    }

    /*
    * If we reach here with `tab' null, it can only be because
    * there was a missing entry in the Huffman table. This
    * should never occur even with invalid input data, because
    * we enforce at mktable time that the Huffman codes should
    * precisely cover the code space; so we can enforce this
    * by assertion.
    */
    assert(tab);
  }
}

static void emit_char(deflate_decompress_ctx *dctx, int c)
{
  dctx->window[dctx->winpos] = c;
  dctx->winpos = (dctx->winpos + 1) & (DWINSIZE - 1);
  if (dctx->outlen >= dctx->outsize) {
    dctx->outsize = dctx->outlen * 3 / 2 + 512;
    dctx->outblk = sresize(dctx->outblk, dctx->outsize, unsigned char);
  }
  if (dctx->type == DEFLATE_TYPE_ZLIB) {
    unsigned char uc = c;
    dctx->checksum = adler32_update(dctx->checksum, &uc, 1);
  } else if (dctx->type == DEFLATE_TYPE_GZIP) {
    unsigned char uc = c;
    dctx->checksum = crc32_update(dctx->checksum, &uc, 1);
  }
  dctx->outblk[dctx->outlen++] = c;
  dctx->bytesout++;
}

#define EATBITS(n) ( dctx->nbits -= (n), dctx->bits >>= (n) )

int deflate_decompress_data(deflate_decompress_ctx *dctx,
                            const void *vblock, int len,
                            void **outblock, int *outlen)
{
  const coderecord *rec;
  const unsigned char *block = (const unsigned char *)vblock;
  int code, bfinal, btype, rep, dist, nlen, header;
  unsigned long cksum;
  int error = 0;

  if (len == 0) {
    *outblock = NULL;
    *outlen = 0;
    if (dctx->state != FINALSPIN)
      return DEFLATE_ERR_UNEXPECTED_EOF;
    else
      return 0;
  }

  dctx->outblk = NULL;
  dctx->outsize = 0;
  dctx->outlen = 0;

  while (len > 0 || dctx->nbits > 0) {
    while (dctx->nbits < 24 && len > 0) {
      dctx->bits |= (*block++) << dctx->nbits;
      dctx->nbits += 8;
      len--;
#ifdef ANALYSIS
      dctx->bytesread++;
#endif
    }
    switch (dctx->state) {
case ZLIBSTART:
  /* Expect 16-bit zlib header. */
  if (dctx->nbits < 16)
    goto finished;	       /* done all we can */

  /*
  * The header is stored as a big-endian 16-bit integer,
  * in contrast to the general little-endian policy in
  * the rest of the format :-(
  */
  header = (((dctx->bits & 0xFF00) >> 8) |
    ((dctx->bits & 0x00FF) << 8));
  EATBITS(16);

  /*
  * Check the header:
  *
  *  - bits 8-11 should be 1000 (Deflate/RFC1951)
  *  - bits 12-15 should be at most 0111 (window size)
  *  - bit 5 should be zero (no dictionary present)
  *  - we don't care about bits 6-7 (compression rate)
  *  - bits 0-4 should be set up to make the whole thing
  *    a multiple of 31 (checksum).
  */
  if ((header & 0xF000) >  0x7000 ||
    (header & 0x0020) != 0x0000 ||
    (header % 31) != 0) {
      error = DEFLATE_ERR_ZLIB_HEADER;
      goto finished;
  }
  if ((header & 0x0F00) != 0x0800) {
    error = DEFLATE_ERR_ZLIB_WRONGCOMP;
    goto finished;
  }
  dctx->state = OUTSIDEBLK;
  break;
case GZIPSTART:
  /* Expect 16-bit gzip header. */
  if (dctx->nbits < 16)
    goto finished;
  header = dctx->bits & 0xFFFF;
  EATBITS(16);
  if (header != 0x8B1F) {
    error = DEFLATE_ERR_GZIP_HEADER;
    goto finished;
  }
  dctx->state = GZIPMETHFLAGS;
  break;
case GZIPMETHFLAGS:
  /* Expect gzip compression method and flags bytes. */
  if (dctx->nbits < 16)
    goto finished;
  header = dctx->bits & 0xFF;
  EATBITS(8);
  if (header != 8) {
    error = DEFLATE_ERR_GZIP_WRONGCOMP;
    goto finished;
  }
  dctx->gzflags = dctx->bits & 0xFF;
  if (dctx->gzflags & 2) {
    /*
    * The FHCRC flag is slightly confusing. RFC1952
    * documents it as indicating the presence of a
    * two-byte CRC16 of the gzip header, occurring
    * just before the beginning of the Deflate stream.
    * However, gzip itself (as of 1.3.5) appears to
    * believe it indicates that the current gzip
    * `member' is not the final one, i.e. that the
    * stream is composed of multiple gzip members
    * concatenated together, and furthermore gzip will
    * refuse to decode any file that has it set.
    * 
    * For this reason, I label it as `disputed' and
    * also refuse to decode anything that has it set.
    * I don't expect this to be a problem in practice.
    */
    error = DEFLATE_ERR_GZIP_FHCRC;
    goto finished;
  }
  EATBITS(8);
  dctx->state = GZIPIGNORE1;
  break;
case GZIPIGNORE1:
case GZIPIGNORE2:
case GZIPIGNORE3:
  /* Expect two bytes of gzip timestamp/XFL/OS, which we ignore. */
  if (dctx->nbits < 16)
    goto finished;
  EATBITS(16);
  if (dctx->state == GZIPIGNORE3) {
    dctx->state = GZIPEXTRA;
  } else
    dctx->state++;	       /* maps IGNORE1 -> IGNORE2 -> IGNORE3 */
  break;
case GZIPEXTRA:
  if (dctx->gzflags & 4) {
    /* Expect two bytes of extra-length count, then that many
    * extra bytes of header data, all of which we ignore. */
    if (!dctx->gzextralen) {
      if (dctx->nbits < 16)
        goto finished;
      dctx->gzextralen = dctx->bits & 0xFFFF;
      EATBITS(16);
      break;
    } else if (dctx->gzextralen > 0) {
      if (dctx->nbits < 8)
        goto finished;
      EATBITS(8);
      if (--dctx->gzextralen > 0)
        break;
    }
  }
  dctx->state = GZIPFNAME;
  break;
case GZIPFNAME:
  if (dctx->gzflags & 8) {
    /*
    * Expect a NUL-terminated filename.
    */
    if (dctx->nbits < 8)
      goto finished;
    code = dctx->bits & 0xFF;
    EATBITS(8);
  } else
    code = 0;
  if (code == 0)
    dctx->state = GZIPCOMMENT;
  break;
case GZIPCOMMENT:
  if (dctx->gzflags & 16) {
    /*
    * Expect a NUL-terminated filename.
    */
    if (dctx->nbits < 8)
      goto finished;
    code = dctx->bits & 0xFF;
    EATBITS(8);
  } else
    code = 0;
  if (code == 0)
    dctx->state = OUTSIDEBLK;
  break;
case OUTSIDEBLK:
  /* Expect 3-bit block header. */
  if (dctx->nbits < 3)
    goto finished;	       /* done all we can */
  bfinal = dctx->bits & 1;
  if (bfinal)
    dctx->lastblock = TRUE;
  EATBITS(1);
  btype = dctx->bits & 3;
  EATBITS(2);
  if (btype == 0) {
    int to_eat = dctx->nbits & 7;
    dctx->state = UNCOMP_LEN;
    EATBITS(to_eat);       /* align to byte boundary */
  } else if (btype == 1) {
    dctx->currlentable = dctx->staticlentable;
    dctx->currdisttable = dctx->staticdisttable;
    dctx->state = INBLK;
  } else if (btype == 2) {
    dctx->state = TREES_HDR;
  }
  debug(("recv: bfinal=%d btype=%d\n", bfinal, btype));
#ifdef ANALYSIS
  if (analyse_level > 1) {
    static const char *const btypes[] = {
      "uncompressed", "static", "dynamic", "type 3 (unknown)"
    };
    printf("new block, %sfinal, %s\n",
      bfinal ? "" : "not ",
      btypes[btype]);
  }
#endif
  break;
case TREES_HDR:
  /*
  * Dynamic block header. Five bits of HLIT, five of
  * HDIST, four of HCLEN.
  */
  if (dctx->nbits < 5 + 5 + 4)
    goto finished;	       /* done all we can */
  dctx->hlit = 257 + (dctx->bits & 31);
  EATBITS(5);
  dctx->hdist = 1 + (dctx->bits & 31);
  EATBITS(5);
  dctx->hclen = 4 + (dctx->bits & 15);
  EATBITS(4);
  debug(("recv: hlit=%d hdist=%d hclen=%d\n", dctx->hlit,
    dctx->hdist, dctx->hclen));
#ifdef ANALYSIS
  if (analyse_level > 1)
    printf("hlit=%d, hdist=%d, hclen=%d\n",
    dctx->hlit, dctx->hdist, dctx->hclen);
#endif
  dctx->lenptr = 0;
  dctx->state = TREES_LENLEN;
  memset(dctx->lenlen, 0, sizeof(dctx->lenlen));
  break;
case TREES_LENLEN:
  if (dctx->nbits < 3)
    goto finished;
  while (dctx->lenptr < dctx->hclen && dctx->nbits >= 3) {
    dctx->lenlen[lenlenmap[dctx->lenptr++]] =
      (unsigned char) (dctx->bits & 7);
    debug(("recv: lenlen %d\n", (unsigned char) (dctx->bits & 7)));
    EATBITS(3);
  }
  if (dctx->lenptr == dctx->hclen) {
    dctx->lenlentable = mktable(dctx->lenlen, 19,
#ifdef ANALYSIS
      "code length",
#endif
      &error);
    if (!dctx->lenlentable)
      goto finished;     /* error code set up by mktable */
    dctx->state = TREES_LEN;
    dctx->lenptr = 0;
  }
  break;
case TREES_LEN:
  if (dctx->lenptr >= dctx->hlit + dctx->hdist) {
    dctx->currlentable = mktable(dctx->lengths, dctx->hlit,
#ifdef ANALYSIS
      "literal/length",
#endif
      &error);
    if (!dctx->currlentable)
      goto finished;     /* error code set up by mktable */
    dctx->currdisttable = mktable(dctx->lengths + dctx->hlit,
      dctx->hdist,
#ifdef ANALYSIS
      "distance",
#endif
      &error);
    if (!dctx->currdisttable)
      goto finished;     /* error code set up by mktable */
    freetable(&dctx->lenlentable);
    dctx->lenlentable = NULL;
    dctx->state = INBLK;
    break;
  }
  code = huflookup(&dctx->bits, &dctx->nbits, dctx->lenlentable);
  debug(("recv: codelen %d\n", code));
  if (code == -1)
    goto finished;
  if (code < 16) {
#ifdef ANALYSIS
    if (analyse_level > 1)
      printf("code-length %d\n", code);
#endif
    dctx->lengths[dctx->lenptr++] = code;
  } else {
    dctx->lenextrabits = (code == 16 ? 2 : code == 17 ? 3 : 7);
    dctx->lenaddon = (code == 18 ? 11 : 3);
    dctx->lenrep = (code == 16 && dctx->lenptr > 0 ?
      dctx->lengths[dctx->lenptr - 1] : 0);
    dctx->state = TREES_LENREP;
  }
  break;
case TREES_LENREP:
  if (dctx->nbits < dctx->lenextrabits)
    goto finished;
  rep =
    dctx->lenaddon +
    (dctx->bits & ((1 << dctx->lenextrabits) - 1));
  EATBITS(dctx->lenextrabits);
  if (dctx->lenextrabits)
    debug(("recv: codelen-extrabits %d/%d\n", rep - dctx->lenaddon,
    dctx->lenextrabits));
#ifdef ANALYSIS
  if (analyse_level > 1)
    printf("code-length-repeat: %d copies of %d\n", rep,
    dctx->lenrep);
#endif
  while (rep > 0 && dctx->lenptr < dctx->hlit + dctx->hdist) {
    dctx->lengths[dctx->lenptr] = dctx->lenrep;
    dctx->lenptr++;
    rep--;
  }
  dctx->state = TREES_LEN;
  break;
case INBLK:
#ifdef ANALYSIS
  dctx->bitcount_before = BITCOUNT(dctx);
#endif
  code = huflookup(&dctx->bits, &dctx->nbits, dctx->currlentable);
  debug(("recv: litlen %d\n", code));
  if (code == -1)
    goto finished;
  if (code < 256) {
#ifdef ANALYSIS
    if (analyse_level > 0)
      printf("%lu: literal %d [%d]\n", dctx->bytesout, code,
      BITCOUNT(dctx) - dctx->bitcount_before);
#endif
    emit_char(dctx, code);
  } else if (code == 256) {
    if (dctx->lastblock)
      dctx->state = END;
    else
      dctx->state = OUTSIDEBLK;
    if (dctx->currlentable != dctx->staticlentable) {
      freetable(&dctx->currlentable);
      dctx->currlentable = NULL;
    }
    if (dctx->currdisttable != dctx->staticdisttable) {
      freetable(&dctx->currdisttable);
      dctx->currdisttable = NULL;
    }
  } else if (code < 286) {   /* static tree can give >285; ignore */
    dctx->state = GOTLENSYM;
    dctx->sym = code;
  }
  break;
case GOTLENSYM:
  rec = &lencodes[dctx->sym - 257];
  if (dctx->nbits < rec->extrabits)
    goto finished;
  dctx->len =
    rec->min + (dctx->bits & ((1 << rec->extrabits) - 1));
  if (rec->extrabits)
    debug(("recv: litlen-extrabits %d/%d\n",
    dctx->len - rec->min, rec->extrabits));
  EATBITS(rec->extrabits);
  dctx->state = GOTLEN;
  break;
case GOTLEN:
  code = huflookup(&dctx->bits, &dctx->nbits, dctx->currdisttable);
  debug(("recv: dist %d\n", code));
  if (code == -1)
    goto finished;
  dctx->state = GOTDISTSYM;
  dctx->sym = code;
  break;
case GOTDISTSYM:
  rec = &distcodes[dctx->sym];
  if (dctx->nbits < rec->extrabits)
    goto finished;
  dist = rec->min + (dctx->bits & ((1 << rec->extrabits) - 1));
  if (rec->extrabits)
    debug(("recv: dist-extrabits %d/%d\n",
    dist - rec->min, rec->extrabits));
  EATBITS(rec->extrabits);
  dctx->state = INBLK;
#ifdef ANALYSIS
  if (analyse_level > 0)
    printf("%lu: copy len=%d dist=%d [%d]\n", dctx->bytesout,
    dctx->len, dist,
    BITCOUNT(dctx) - dctx->bitcount_before);
#endif
  while (dctx->len--)
    emit_char(dctx, dctx->window[(dctx->winpos - dist) &
    (DWINSIZE - 1)]);
  break;
case UNCOMP_LEN:
  /*
  * Uncompressed block. We expect to see a 16-bit LEN.
  */
  if (dctx->nbits < 16)
    goto finished;
  dctx->uncomplen = dctx->bits & 0xFFFF;
  EATBITS(16);
  dctx->state = UNCOMP_NLEN;
  break;
case UNCOMP_NLEN:
  /*
  * Uncompressed block. We expect to see a 16-bit NLEN,
  * which should be the one's complement of the previous
  * LEN.
  */
  if (dctx->nbits < 16)
    goto finished;
  nlen = dctx->bits & 0xFFFF;
  EATBITS(16);
  if (dctx->uncomplen == 0)
    dctx->state = OUTSIDEBLK;	/* block is empty */
  else
    dctx->state = UNCOMP_DATA;
  break;
case UNCOMP_DATA:
  if (dctx->nbits < 8)
    goto finished;
#ifdef ANALYSIS
  if (analyse_level > 0)
    printf("%lu: uncompressed %d [8]\n", dctx->bytesout,
    (int)(dctx->bits & 0xFF));
#endif
  emit_char(dctx, dctx->bits & 0xFF);
  EATBITS(8);
  if (--dctx->uncomplen == 0)
    dctx->state = OUTSIDEBLK;	/* end of uncompressed block */
  break;
case END:
  /*
  * End of compressed data. We align to a byte boundary,
  * and then look for format-specific trailer data.
  */
  {
    int to_eat = dctx->nbits & 7;
    EATBITS(to_eat);
  }
  if (dctx->type == DEFLATE_TYPE_ZLIB)
    dctx->state = ADLER1;
  else if (dctx->type == DEFLATE_TYPE_GZIP)
    dctx->state = CRC1;
  else
    dctx->state = FINALSPIN;
  break;
case ADLER1:
  if (dctx->nbits < 16)
    goto finished;
  cksum = (dctx->bits & 0xFF) << 8;
  EATBITS(8);
  cksum |= (dctx->bits & 0xFF);
  EATBITS(8);
  if (cksum != ((dctx->checksum >> 16) & 0xFFFF)) {
    error = DEFLATE_ERR_CHECKSUM;
    goto finished;
  }
  dctx->state = ADLER2;
  break;
case ADLER2:
  if (dctx->nbits < 16)
    goto finished;
  cksum = (dctx->bits & 0xFF) << 8;
  EATBITS(8);
  cksum |= (dctx->bits & 0xFF);
  EATBITS(8);
  if (cksum != (dctx->checksum & 0xFFFF)) {
    error = DEFLATE_ERR_CHECKSUM;
    goto finished;
  }
  dctx->state = FINALSPIN;
  break;
case CRC1:
  if (dctx->nbits < 16)
    goto finished;
  cksum = dctx->bits & 0xFFFF;
  EATBITS(16);
  if (cksum != (dctx->checksum & 0xFFFF)) {
    error = DEFLATE_ERR_CHECKSUM;
    goto finished;
  }
  dctx->state = CRC2;
  break;
case CRC2:
  if (dctx->nbits < 16)
    goto finished;
  cksum = dctx->bits & 0xFFFF;
  EATBITS(16);
  if (cksum != ((dctx->checksum >> 16) & 0xFFFF)) {
    error = DEFLATE_ERR_CHECKSUM;
    goto finished;
  }
  dctx->state = ILEN1;
  break;
case ILEN1:
  if (dctx->nbits < 16)
    goto finished;
  cksum = dctx->bits & 0xFFFF;
  EATBITS(16);
  if (cksum != (dctx->bytesout & 0xFFFF)) {
    error = DEFLATE_ERR_INLEN;
    goto finished;
  }
  dctx->state = ILEN2;
  break;
case ILEN2:
  if (dctx->nbits < 16)
    goto finished;
  cksum = dctx->bits & 0xFFFF;
  EATBITS(16);
  if (cksum != ((dctx->bytesout >> 16) & 0xFFFF)) {
    error = DEFLATE_ERR_INLEN;
    goto finished;
  }
  dctx->state = FINALSPIN;
  break;
case FINALSPIN:
  /* Just ignore any trailing garbage on the data stream. */
  /* (We could alternatively throw an error here, if we wanted
  * to detect and complain about trailing garbage.) */
  EATBITS(dctx->nbits);
  break;
    }
  }

finished:
  *outblock = dctx->outblk;
  *outlen = dctx->outlen;
  return error;
}

#define A(code,str) str
const char *const deflate_error_msg[DEFLATE_NUM_ERRORS] = {
  DEFLATE_ERRORLIST(A)
};
#undef A

#define A(code,str) #code
const char *const deflate_error_sym[DEFLATE_NUM_ERRORS] = {
  DEFLATE_ERRORLIST(A)
};
#undef A

#ifdef STANDALONE

int main(int argc, char **argv)
{
  unsigned char buf[65536];
  void *outbuf;
  int ret, err, outlen;
  deflate_decompress_ctx *dhandle;
  deflate_compress_ctx *chandle;
  int type = DEFLATE_TYPE_ZLIB, opts = TRUE;
  int compress = FALSE, decompress = FALSE;
  int got_arg = FALSE;
  char *filename = NULL;
  FILE *fp;

  while (--argc) {
    char *p = *++argv;

    got_arg = TRUE;

    if (p[0] == '-' && opts) {
      if (!strcmp(p, "-b"))
        type = DEFLATE_TYPE_BARE;
      else if (!strcmp(p, "-g"))
        type = DEFLATE_TYPE_GZIP;
      else if (!strcmp(p, "-c"))
        compress = TRUE;
      else if (!strcmp(p, "-d"))
        decompress = TRUE;
      else if (!strcmp(p, "-a"))
        analyse_level++, decompress = TRUE;
      else if (!strcmp(p, "--"))
        opts = FALSE;          /* next thing is filename */
      else {
        fprintf(stderr, "unknown command line option '%s'\n", p);
        return 1;
      }
    } else if (!filename) {
      filename = p;
    } else {
      fprintf(stderr, "can only handle one filename\n");
      return 1;
    }
  }

  if (!compress && !decompress) {
    fprintf(stderr, "usage: deflate [ -c | -d | -a ] [ -b | -g ]"
      " [filename]\n");
    return (got_arg ? 1 : 0);
  }

  if (compress && decompress) {
    fprintf(stderr, "please do not specify both compression and"
      " decompression\n");
    return (got_arg ? 1 : 0);
  }

  if (compress) {
    chandle = deflate_compress_new(type);
    dhandle = NULL;
  } else {
    dhandle = deflate_decompress_new(type);
    chandle = NULL;
  }

  if (filename)
    fp = fopen(filename, "rb");
  else
    fp = stdin;

  if (!fp) {
    assert(filename);
    fprintf(stderr, "unable to open '%s'\n", filename);
    return 1;
  }

  do {
    ret = fread(buf, 1, sizeof(buf), fp);
    outbuf = NULL;
    if (dhandle) {
      if (ret > 0)
        err = deflate_decompress_data(dhandle, buf, ret,
        (void **)&outbuf, &outlen);
      else
        err = deflate_decompress_data(dhandle, NULL, 0,
        (void **)&outbuf, &outlen);
    } else {
      if (ret > 0)
        deflate_compress_data(chandle, buf, ret, DEFLATE_NO_FLUSH,
        (void **)&outbuf, &outlen);
      else
        deflate_compress_data(chandle, buf, ret, DEFLATE_END_OF_DATA,
        (void **)&outbuf, &outlen);
      err = 0;
    }
    if (outbuf) {
      if (!analyse_level && outlen)
        fwrite(outbuf, 1, outlen, stdout);
      sfree(outbuf);
    }
    if (err > 0) {
      fprintf(stderr, "decoding error: %s\n", deflate_error_msg[err]);
      return 1;
    }
  } while (ret > 0);

  if (dhandle)
    deflate_decompress_free(dhandle);
  if (chandle)
    deflate_compress_free(chandle);

  if (filename)
    fclose(fp);

  return 0;
}

#endif

#ifdef TESTMODE

int main(int argc, char **argv)
{
  char *filename = NULL;
  FILE *fp;
  deflate_compress_ctx *chandle;
  deflate_decompress_ctx *dhandle;
  unsigned char buf[65536], *outbuf, *outbuf2;
  int ret, err, outlen, outlen2;
  int dlen = 0, clen = 0;
  int opts = TRUE;

  while (--argc) {
    char *p = *++argv;

    if (p[0] == '-' && opts) {
      if (!strcmp(p, "--"))
        opts = FALSE;          /* next thing is filename */
      else {
        fprintf(stderr, "unknown command line option '%s'\n", p);
        return 1;
      }
    } else if (!filename) {
      filename = p;
    } else {
      fprintf(stderr, "can only handle one filename\n");
      return 1;
    }
  }

  if (filename)
    fp = fopen(filename, "rb");
  else
    fp = stdin;

  if (!fp) {
    assert(filename);
    fprintf(stderr, "unable to open '%s'\n", filename);
    return 1;
  }

  chandle = deflate_compress_new(DEFLATE_TYPE_ZLIB);
  dhandle = deflate_decompress_new(DEFLATE_TYPE_ZLIB);

  do {
    ret = fread(buf, 1, sizeof(buf), fp);
    if (ret <= 0) {
      deflate_compress_data(chandle, NULL, 0, DEFLATE_END_OF_DATA,
        (void **)&outbuf, &outlen);
    } else {
      dlen += ret;
      deflate_compress_data(chandle, buf, ret, DEFLATE_NO_FLUSH,
        (void **)&outbuf, &outlen);
    }
    if (outbuf) {
      clen += outlen;
      err = deflate_decompress_data(dhandle, outbuf, outlen,
        (void **)&outbuf2, &outlen2);
      sfree(outbuf);
      if (outbuf2) {
        if (outlen2)
          fwrite(outbuf2, 1, outlen2, stdout);
        sfree(outbuf2);
      }
      if (!err && ret <= 0) {
        /*
        * signal EOF
        */
        err = deflate_decompress_data(dhandle, NULL, 0,
          (void **)&outbuf2, &outlen2);
        assert(outbuf2 == NULL);
      }
      if (err) {
        fprintf(stderr, "decoding error: %s\n",
          deflate_error_msg[err]);
        return 1;
      }
    }
  } while (ret > 0);

  fprintf(stderr, "%d plaintext -> %d compressed\n", dlen, clen);

  return 0;
}

#endif
